''Rhithropanopeus harrisii'' (

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

s include the Zuiderzee crab, dwarf crab, estuarine mud crab, Harris mud crab, white-fingered mud crab, and white-tipped mud crab), is a small omnivorous

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

native to Atlantic coasts of the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

, from New Brunswick to Veracruz. ''R. harrisii'' is usually found in brackish water, but can also be found in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

. It likes to live on stones and in oyster beds. The crab can reach a maximum size of . It has an olive-green-brownish color, sometimes with dark spots on its

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

. It is a common inhabitant of Texas and Florida estuaries, but was later introduced all over the world. In 1937, it was discovered to be invading the

San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...

's brackish waters and adjacent fresh waters of the

California Central Valley The Central Valley is a broad, elongated, flat valley that dominates the interior of California. It is wide and runs approximately from north-northwest to south-southeast, inland from and parallel to the Pacific coast of the state. It covers ...

. It was also recently discovered in the

Third Lock Lake in Panama The Panama Canal expansion project ( es, ampliación del Canal de Panamá), also called the Third Set of Locks Project, doubled the capacity of the Panama Canal by adding a new lane of traffic allowing for a larger number of ships, and increasin ...

, a man-made lake intended to be a part of the Panama Canal. ''R. harrisii'' was first discovered in Europe in the Zuider Zee, the Netherlands, and is now also found in Denmark, Belgium, Germany, France, Poland, Estonia, Finland, Russia, Portugal, Spain, Italy, Romania and Bulgaria, from the Black Sea and Caspian Sea. In the British Isles, ''R. harrisii'' has only been observed in

Roath Docks Roath ( cy, Y Rhath) is a district and community to the north-east of the city centre of Cardiff, capital of Wales. There is no community council for the area which is mostly covered by the Plasnewydd electoral ward, and stretches from Ad ...

, Cardiff, which have lower

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

(12 ‰) than the surrounding waters. Breeding

populations have been found in the

Brazos River The Brazos River ( , ), called the ''Río de los Brazos de Dios'' (translated as "The River of the Arms of God") by early Spanish explorers, is the 11th-longest river in the United States at from its headwater source at the head of Blackwater Dr ...

basin in Texas, notably the

Possum Kingdom State Park Possum Kingdom State Park is a state park in Palo Pinto County, Texas, USA, that was built in the 1940s by Civilian Conservation Corps Company 2888 and opened to the public in 1950. It covers approximately , and lies in the Palo Pinto Mountains ...

and

Lake Granbury Lake Granbury is a North Texas reservoir near Granbury, Texas. It was created in 1969 and is one of three lakes damming the Brazos River. Lake Granbury is contained by the De Cordova Bend Dam and is a long, narrow lake, encompassed by 103 mile ...

. Populations have also been discovered in Lake Texoma and

Lake E.V. Spence E.V. Spence Reservoir (also known as Lake E.V. Spence) is an artificial lake located west of (and upstream from) the town of Robert Lee, Texas. The reservoir was impounded by the creation of Robert Lee Dam in 1969, with the support of the Upper ...

. Its presence in the Baltic Sea is blamed for a negative ecosystem shift. A record of this species was made in Brazil, but might represent a misidentification.

References

Xanthoidea Crustaceans of the Atlantic Ocean Crustaceans described in 1841 Taxa named by Augustus Addison Gould {{crustacean-stub